Spinal fixation systems which are used to correct spinal deformities and treat spinal degenerations generally include a plurality of bone fixation elements anchored in, for example, the pedicle of adjacent vertebrae. The bone fixation elements are interconnected to one another by, for example, one or more elongated spinal rods. In order to access the spinal area for implantation of these spinal fixation systems and their individual components, open approach surgical techniques have traditionally been employed. These open procedures generally involve large skin incisions and extensive tissue retraction and resection, all which may result in considerable post-operative pain and prolonged recovery time.
More recently, surgeons have used minimally invasive techniques to reduce the post-operative effects of spinal fixation procedures. A paraspinal approach is one form of minimally invasive technique and involves muscle splitting or muscle sparing in order to gain access to the posterior elements of the spine. Such a technique minimizes trauma to tissues adjacent the spine. Unlike open procedures where muscles and other soft tissue are cut, split, stripped and dissected, the paraspinal approach involves separation or splitting of the muscles along their fibers.
Implanting a spinal rod fixation system generally involves at least two steps: (i) placing bone fixation elements into the spine and (ii) inserting a rod between the bone fixation elements. Bone fixation elements generally include a screw portion and a body portion. The screw portion is inserted into the spine and the body portion generally includes a rod-receiving channel for receiving and securing the spinal rod. The rod may be inserted through an incision in the skin, which may be separate and distinct from the incision through which the bone fixation element(s) is placed. Alternatively, the rod may be inserted through the same incision as the bone fixation element(s).
It is desirable to have a minimally invasive bone fixation element and rod introduction system which minimizes trauma to the body, provides for simplified and time saving instrumentation for rod reduction, enables a rod to be readily connected to multiple bone fixation elements anchored at varying depths in the body, is generally simple to use, enhances direct visualization of the rod as the rod is being inserted into the bone fixation elements and facilitates securement of the rod to the bone fixation elements.